1. Field of the Invention
The present invention relates to a processing apparatus for removing a processing agent from a peripheral portion of a substrate such as an LCD substrate, a semiconductor wafer, etc.
2. Description of the Related Art
In the manufacturing process of liquid crystal display (LCD), semiconductor device, etc., so-called lithography process is executed to form resist film patterns on an upper surface of an LCD substrate or a semiconductor wafer serving as a substrate. The lithography process includes various process steps such as substrate cleaning, substrate drying, resist coating on a substrate surface, exposure/development of a photosensitive film, etc. For instance, after the substrate has been cleaned, hydrophobicity process is executed and, after the substrate has been cooled, a photosensitive film is formed on a surface of the substrate by coating the resist as photoresist. Then, after baking process has been applied by heating the substrate, predetermined patterns are exposed on the photosensitive film by the exposure unit, then a liquid developer is coated/developed on the surface of the substrate which has been subjected to the exposure process, and then the liquid developer is rinsed by a rinsing solution, whereby the developing process has been completed.
In the above lithography process, a spin coating method, a spray method, etc. have been employed as resist coating process. If the resist is coated according to these methods, a film thickness is uniform immediately after coating, nevertheless the resist becomes thick like a risen portion on the peripheral portion of the substrate due to an influence of a surface tension after a centrifugal force has not operated because of stop of rotation or as the time has lapsed. In addition, there are some cases where the resist which is taken out by rotation is scattered onto a back surface of the substrate to thus adhere to unnecessary areas thereof. Like this, the resist which has been adhered to either the nonuniform thickness portion formed on the peripheral portion of the substrate or the back surface of the substrate would cause generation of particles during carrying process of the substrate, etc. In addition, such resist also causes contamination of carrying units for carrying the substrate.
In the prior art, after the resist has been coated on the substrate by the coating unit, the substrate is transferred to a removing unit wherein unnecessary resist adhered on the peripheral portion of the substrate is removed. In the removing unit, nozzle heads which have their recess portions for injecting the solvent from their insides are provided. The peripheral portion of the substrate is inserted into the recess portions via their clearances. Then, while moving the recess portions along the peripheral portion of the substrate, the solvent is injected from the inside of the recess portions to upper and lower surfaces of the peripheral portion of the substrate to melt the unnecessary resist and then such resist is sucked to be removed outside.
However, since only a central area of the above substrate can be held on a loading table by virtue of vacuum suction but the peripheral portion of the substrate acts as a free end, bowing of the peripheral portion of the substrate occurs after the substrate has been subjected to thermal treatment, etc. As a consequence, there have been some cases where the substrate cannot be inserted into the recess portion because bowed peripheral portion of the substrate strikes against an inlet of the recess portion of the nozzle main body of the above removing unit.
In such case, it may be considered that insertion of the peripheral portion of the substrate can be facilitated by enlarging a clearance of the recess portion. However, if the clearance of the recess portion is enlarged, the solvent being injected from the inside of the recess portion becomes difficult to be sprayed onto the resist, so that an efficiency in removing the resist is reduced. Therefore, it is not preferable to enlarge the clearance of the recess portion.
Besides, it may be thought of that vacuum suction of the substrate should be applied from the central area to the peripheral area of the substrate on the loading table to prevent the bowing of the substrate. However, if the peripheral portion of the substrate placed on the loading table is sucked by vacuum, it is likely that, when the substrate on the loading table is transferred from the loading table to a main arm used to pass the substrate to various processor units, the loading table would interfere with such main arm. As a result, it is evident that vacuum suction extending up to the peripheral portion of the substrate would not preferable.
In the meanwhile, according to kinds of the resist, there have been some cases where the resist on the peripheral portion of the substrate cannot be perfectly removed only by supplying the solvent to the resist. In the prior art, it has been requested to take a countermeasure against such case.